1. Field
The present disclosure relates generally to telecommunications, and specifically to power saving modes in wireless devices.
2. Background
The deployment of wireless local area networks (WLANs) in the home, the office, and various public facilities is commonplace today. These networks typically employ a wireless access point (AP) that connects a number of wireless stations (STAs) in a specific locality (e.g., home, office, public facility, etc.) to another network, such as the Internet or the like.
STAs that operate in an IEEE 802.11 compliant WLAN use carrier sensing multiple access (CSMA or CSMA-CA) to access the wireless channel. CSMA is a media access control (MAC) protocol that ensures that only one STA has access to the wireless channel at a time. Specifically, only one of the STAs is permitted to exchange data with the AP during any given interval. Meanwhile, the other STAs “listen” to the channel to determine if and when the channel is available. Thus, STAs often experience a substantial amount of “idle” time (e.g., wherein the STAs are not transmitting and/or receiving data) while connected to a network. To save power, many STAs are configured to enter into a “sleep” state when the idle time exceeds a threshold period. The sleep state is a low power mode in which transmitter, receiver, and/or other internal components are temporarily powering down.
The AP periodically broadcasts beacon frames to enable any STA within range to establish and/or maintain a connection with the Wi-Fi network. Each beacon frame includes a traffic indication map (TIM) specifying which STAs in the network, if any, have downlink data waiting in the AP's queue. Thus, to ensure that the STA does not miss any incoming data, it periodically wakes up from the sleep state to listen for beacon frames broadcast by the AP. The STA may also wake from the sleep state when it has uplink data for the AP in its queue. Once awaken to receive or transmit data, the STA will return to the sleep state only after it has been idle for another threshold period.
STAs that operate in an IEEE 802.11 compliant WLAN, as well as other similar devices, can experience significant power savings by entering into a sleep state when inactive. However, further power savings may be achieved with more efficient algorithms for controlling the sleep state of the device.